1. Field of the Invention
The present invention relates to an improved system for emulsifying milk or other dairy-based liquids with other fluids and dispensing them for ultimate consumption in a hot beverage. The invention has particular applicability in the preparation of hot dairy-based beverages such as hot chocolate, cappuccino, coffee latte, flavored steamers (heated flavored milk), and other hot beverages containing dairy-based liquids.
2. Description of the Prior Art
Various systems have existed for quite a number of years for emulsifying dairy-based liquids, such as milk, with other fluids in the preparation of hot beverages. For example, U.S. Pat. No. 4,715,274 describes an emulsifier unit for emulsifying steam, air, and milk to prepare such beverages as cappuccino and coffee latte. In the preparation of such beverages steam and air are mixed with milk or cream in a venturi-type emulsification chamber and dispensed from this device, such as for mixing with coffee. The portions of steam and air that are mixed with the milk vary, depending upon the particular hot beverage desired. For example, cappuccino requires an aerated mixture of milk and air. Typically, this mixture is comprised of about two-thirds milk and about one-third air by volume. About half of the milk in a portion suitable for making cappuccino coffee is in a liquid form, while the other half is in the form of foam above the liquid. The milk and air is emulsified and heated with steam in the emulsification chamber and preferably dispensed at a temperature between 155° F. and 165° F. The steam is typically under a pressure of about fifteen to twenty-two pounds per square inch above ambient atmospheric pressure and is preferably injected into the emulsification chamber at 120° C.–125° C.
In making a coffee latte drink, on the other hand, only heated milk is employed, and air is not mixed with the milk and steam in the emulsification chamber. To the contrary, the air supply is completely shut off. The hot milk is preferably dispensed at a temperature of between 155° F. and 165° F.
Conventional emulsification systems for creating milk-based beverages, such as cappuccino and coffee latte, have a number of disadvantages. Specifically, conventional systems rely upon drawing the air and milk into the emulsification system due to the suctional force that results from a venturi effect in the emulsification chamber. Sometimes the flow of milk is aided by a pump. The milk is typically drawn from a separate, refrigerated supply location, at roughly the same or a lower level of elevation as the emulsification unit. The milk is sucked through a tube emanating from the top of the milk container and connected into the venturi inlet of the emulsifier unit. Another air inlet to the venturi system draws in ambient air. Suctional force is created by injecting steam under pressure through the venturi, whereby the rapid flow at the constriction of the venturi creates suctional force that is exerted on the milk, and in the case of cappuccino, on ambient air as well.
Conventional milk-based beverage dispensing systems based on venturi-induced emulsification of the type used in the preparation of cappuccino and coffee latte are notoriously inconsistent and temperamental. The temperature of the beverages dispensed in such systems fluctuates considerably, thereby varying the quality of the drink. In conventional systems the cold storage chamber for the milk is located next to, behind, and/or below the emulsifier. Consequently, as the level of milk within the container drops as beverages are dispensed, the amount of milk drawn in by the suction of the venturi drops as well, thus leading to inconsistent quantities of milk dispensed relative to the air drawn into the unit. Conventional systems employ suction and siphoning that is created solely by the subatmospheric pressure created and sustained by a venturi-based emulsifier, sometimes termed a foamer head.
Also, conventional systems involve milk flow through a number of components in the automated mixing system. For sanitation reasons applicable to food preparation establishments, cleaning of each and every component of the emulsifying, beverage dispensing unit with which milk or any other dairy product makes contact must occur on a daily basis. The NSF (National Sanitary Foundation) sets the standards in this regard in this country. The cleaning process is quite time consuming. Also, the individuals employed to perform the cleaning task often do so with different degrees of thoroughness. If cleaning is not performed according to existing specifications each time for each machine, the temperature at which the steam heated, milk-based beverage is dispensed and the air/milk ratio (for foamy milk) of the mixture becomes rather inconsistent.
Another problem that occurs in conventional venturi-based emulsification systems is that the temperature at which nonfoamy steamed milk is dispensed, such as for use in coffee latte, is lower than the temperature at which foamy steamed milk is dispensed. This is due to the fact that conventional emulsification systems maintain their steam supply (i.e. energy), fixed at one level for both beverages, whereas the mass of liquid that needs to be heated for foamy hot milk is less than the mass for nonfoamy hot milk, (per liquid ounce dispensed). This results in different temperatures for each mixture type. In some automated cappuccino and coffee latte dispensing systems this temperature differential is resolved by equipping the milk supply line or lines with different flow restrictors to regulate the milk flow and therefore the available mass to be heated. These prior systems create a redundancy in expense, have complicated plumbing systems to supply steam and milk to the venturi-based emulsifier unit, and are therefore difficult to assemble, disassemble, and clean.